At about three minutes after the aircraft reached its cruising altitude of 38,000 feet, the captain left the cockpit.

Within 30 seconds of the captain leaving the cockpit, the first officer commanded the aircraft to descend to 100 feet, which is well below ground level.

Within five minutes of the commanded altitude change, the airspeed was changed at least ten times, reaching a maximum of 350 knots (402 mph, 648 kph).

The descent rate reached a maximum of 5,000 feet per minute, and averaged about 3,500 feet per minute.

The descent was continuous, and controlled by the autopilot.

Air traffic controllers and the French military attempted to contact the aircraft several times, but received no response.

Before the collision with the terrain, there were multiple aural warnings heard on the CVR.

The aircraft impacted the ground about 10 minutes and 13 seconds after the aircraft started its descent.

Autopilot and autothrust remained engaged until impact.

On the previous flight, while the captain was out of the cockpit, the first officer twice commanded the aircraft to descend to 100 feet for short periods of time.

The role of the first officer in the crashThe preliminary report did not state a definitive cause of the crash, but it did state that during the cruise phase, the first officer was alone in the cockpit and intentionally modified the autopilot instructions to order the aircraft to descend until it collided with the ground. The report also stated that the first officer did not open the cockpit door during the descent, despite requests for access made via the keypad, with cabin interphone, and by knocking on the door.

Aircraft trajectory(click to enlarge)

First officer training historyThe preliminary report provided an outline of the first officer's training history, including the fact that he started his flight training at the Lufthansa Flight Training Pilot School in Germany on 1 September 2008, but that his training was suspended for medical reasons for over eight months, from 5 November 2008 to 26 August 2009. It was during this period, specifically from April to July 2009, that the first officer did not have a valid medical certificate due to depression and his medical treatment for his condition.

From October 2010 to March 2011, he continued his flight training in the US, but was under contract as a flight attendant with Lufthansa for over two years before beginning his training to become an A320 first officer. He was appointed as an A320 copilot in June 2014.